JPS59185034A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To reproduce a code with accurate pulse width without containing phase jitter component by making a reference voltage of a comparator coincident with a level of zero cross point of eye pattern of the output signal of a waveform equalizer even if the level of this zero cross point is changed due to change in sensitivity. CONSTITUTION:The amplitude versus frequency characteristic in an optical recording and reproducing system of a reproducing signal from an optical disc outputted from a preamplifier is corrected by a waveform equalizer 14 and the output of the waveform equalizer is inputted to a + input terminal of a comparator 15. That is, an output signal of a band pass filter 21 is inputted to a detecting circuit detecting the level of the zero cross point of eye pattern via an impedance converter comprising a transistor 22, a bipolar rectified output voltage is added by resistors 24, 24' and an average value level is outputted. This output is inputted to an operational amplifier 27 to correct the attenuation of the amplitude because of the detecting circuit and also apply a fixed DC voltage 28, thereby attaining minute adjustment of a reference voltage. This reference voltage is the average level of the signal amplitude of a frequency component between minimum inverting intervals and represents the level of zero cross point of the eye pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording and reproducing apparatus that focuses a laser beam into a minute spot light and applies a thermal change to an optical disk to record and reproduce signals.

Conventional configuration and problems thereof In recent years, it has been practiced to focus a laser beam to about 1 .mu.m to record and reproduce a signal on an optical disk.

In particular, devices have come into use that record by depositing a recording material onto an optical disk and applying a thermal change to it using a laser beam.

An example of the conventional optical recording/reproducing apparatus as described above will be described below with reference to the drawings. FIG. 1 shows the configuration of a conventional optical recording/reproducing apparatus. A laser beam from a semiconductor laser 1 is converted into a parallel beam by a condenser lens 2, and is incident on a diaphragm lens 5 by a total reflection mirror 4. Aperture lens 5 directs incident light to optical disk 8 with a diameter of 1μ
Narrow down to a spot as small as 1 μm. The reflected light from the optical filter 8 is again passed through the aperture lens 5. The light is guided to a beam splitter 3 by a total reflection mirror 4 and received by a photodetector 6. A disk motor 7 rotates the disk 8. A preamplifier 9 amplifies the photodetector output signal and inputs it to the demodulator 11 via the signal processing circuit 1o. Reference numeral 12 denotes a semiconductor laser drive circuit which drives the semiconductor laser 1 at a current value such that its optical output exceeds the sensitivity of the recording material in accordance with the signal from the modulator 13. FIG. 2 shows the configuration of the signal processing circuit 1o of FIG. 1. 14 indicates a waveform fixture.

Assuming that the minimum inversion interval of a recording signal is T, the digital signal recorded on an optical disk is T, 2T.

A digital code string having a pulse width of 3T...nT is considered. Such a code string is recorded on an optical disk, and the reproduced signal, that is, the preamplifier output, has frequency characteristics as shown in Figure 3, where the horizontal axis is the pulse width of the code to be recorded, and the vertical axis is the maximum pulse width to be recorded. It represents the signal amplitude of the preamplifier output normalized by the reproduced signal amplitude at nT. A waveform equalizer 14 is provided to correct such amplitude changes due to frequency. The amplitude corrected by the waveform equalization 514 is compared with a fixed reference voltage 16 by a voltage comparator 15, and is converted into a pulse with a sign H2.

This pulse enters the demodulator 11 and undergoes demodulation. Figure 4 is a diagram showing the eye pattern of Nami'J Sugi Toihi's 咉debu 1 (Shokan). T is inn;
represents the group '1-V-voltage compared to above. In this way, it is necessary to set the reference voltage so as to slice the zero crossing point of eye 7<turn. When slicing deviates from the zero crossing point] (phase jitter occurs in the pulse output, and the precise interval 1
ゞT i! l寅f:l', you will no longer be able to do it. If the waveform equalization type output Buch waveform 711x' shows an ideal eye/turn as shown in FIG. A fixed electricity line is fine. However, in reality, optical disk 1
This zero-crossing point M (7) level is not constant but changes due to differences in self-recording sensitivity or changes in recording power. Also (immediately after the recording of Fi, the level l of this zero intersection
)・As time passes, it becomes localized almost at the center of the equalizer output's eye/S turn. Such a phenomenon is often seen on optical discs that perform recording using thermal changes. Figures 5 (ta) to (1) show changes in the amplitude waveform of the preamplifier output as time passes from immediately after recording. Figure 6 shows the bits when the signal was recorded while tracking the guide trunk 19. 5 is a diagram showing a change in the shape of . The waveform of the hatched part 18 in FIG. 5 shows the signal amplitude with the minimum inversion interval T. The waveform diagram of FIG. In this way, as time passes from immediately after recording, the data changes from (a) to (b), (C), (
d). This is because the duty of a bit of a high same wave number component element immediately after recording is smaller than 5Q%, and as time passes, the bit size grows and the duty approaches 50%. Figure 6 shows the growth process of this pinto, and 20 is the hinodo. The horizontal shapes of the waveforms (al to (e) in FIG. 6) correspond to ta) to (6) in FIG. Figure S (e
).

FIG. 6 te+ shows a state where the bit duty exceeds 50% due to poor recording power settings or variations in sensitivity of the recording material of the optical disc.

5 and 6 show changes over time immediately after recording, as well as changes due to changes in recording light power and sensitivity of the recording material. The closer it gets to (a), the more the recording light power is relatively small or the sensitivity of the recording material is low, and the closer it gets to +8), the more the recording light power is relatively large or the sensitivity of the recording material is high. It shows.

Figure 7 (a) - (el+ is Figure 5 (a) - (6), 6
Eye patterns corresponding to the waveforms and bit shapes shown in FIGS. (a) to (e) are shown. As can be understood from FIG. 7, the level of the zero crossing point of the eye pattern changes due to the passage of time immediately after recording, changes in the recording light power, and changes in the sensitivity of the recording material. Such a level change at the zero crossing point is a phenomenon that cannot be observed in optical recording using thermal changes.

If a waveform whose zero crossing level changes as shown in Figures 7 (a) to (6) K is compared with a constant reference voltage such as 16 VC and then output as a pulse, a pulse as shown in Figure 7 Ta is generated. This changes the width and includes a phase jitter component. If a pulse code string containing such a phase jitter component is demodulated, the clock component of the code may not be reproduced or a read error may occur, resulting in a decrease in the reliability of recorded data.

Purpose of the Invention The present invention eliminates the above-mentioned drawbacks and improves the time lapse immediately after recording.
Even if the level of the zero crossing point of the eye pattern of the waveform equalizer output signal changes due to a change in the recording light power or a change in the sensitivity of the recording material, the reference voltage of the comparator is made to match the level of this zero crossing point, and the phase jitter component is The present invention provides an optical recording/reproducing device capable of reproducing a code with an accurate pulse width without any pulse width.

Structure of the Invention The present invention provides means for recording and reproducing signals by focusing a laser beam into a minute spot light and applying a thermal change to an optical disk, and a waveform equalizer for equalizing the waveform of a reproduced signal obtained from the optical disk. and means for using the detection output of a specific frequency component included in the output signal of the waveform equalizer as a reference voltage of a comparator that binarizes the output signal of the waveform equalizer. Even if the level of the zero crossing point of the eye pattern of the waveform equalizer output signal changes due to the passage of time immediately after recording, changes in the recording light power, or changes in the sensitivity of the recording material, the reference voltage of the comparator remains unchanged. By matching the level to the zero crossing point, it is possible to reproduce a code of exactly two pan widths without phase jitter components.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 8 shows the configuration of a signal processing section of an optical recording/reproducing apparatus in an embodiment of the present invention. In FIG. 8, 9 is a preamplifier, 14 is a waveform equalizer, 15 is a comparator, and 11 is a demodulator, which is the same as the configuration shown in FIG. 2. The waveform equalizer 14 corrects the amplitude frequency characteristics of the reproduced signal from the optical disc outputted from the preamplifier in the optical recording/reproducing system. The output of this waveform ring 1 is inputted to the output of the comparator 15.

-The reference voltage generation circuit, which is the central part of the power tree invention, will be explained below. The waveform equalizer output signal outputs only the frequency component of the minimum inversion interval T of the code included in the reproduced signal by the bandpass filter 21. This component is the minimum reversal interval T of the eye pattern explained in FIG.
It represents the time width between zero crossing points of the eye pattern.

It is set. The output signal of the bandpass filter 21 passes through an impedance converter using a transistor 22,
The signal is input to a detection circuit that detects the level of the zero crossing point of the eye pattern. 23 evenings” iodes, 25 capacitors,
The resistor 26 rectifies the waveform in the positive direction, and the resistor 23'
Rectification in the negative direction is performed by the diode 26', the capacitor 26', and the resistor 26'.The rectified output voltages in both the positive and negative directions are added by the resistor 24 and 24', and the average level is output.

This output is input to an operational amplifier 27, and a fixed DC voltage 28 is applied at the same time as the amplitude attenuation caused by the detection circuit is corrected, so that the reference voltage can be finely adjusted. The reference voltage generated in this manner is the average level of the signal amplitude of the frequency component of the minimum inversion interval T, and represents the level of the zero crossing point of the eye pattern.

FIGS. 9A to 9D are diagrams showing signal waveforms at each point in FIGS. 8A and 8D. A shows the output waveform of the preamplifier, 18
The hatched part indicates the signal amplitude at the minimum inversion interval T. As explained in FIG. 5, A shows how the average level of the signal waveform with the minimum inversion interval T moves upwards of the entire signal waveform as time passes from immediately after recording.

B is the waveform equalizer output, and as shown by the hatched part at 30, the signal amplitude of the minimum inversion interval T is corrected from the case of A,
The amplitude is close to that of the entire signal waveform.

C shows the signal waveform after passing through the Ntohas filter, which has the characteristic that the center frequency is -. When this waveform is divided into positive and negative directions, rectified and detected, and resistance is added, the average value level of the signal amplitude of the frequency component of the minimum inversion interval T is obtained as shown in D. By using this D waveform as a reference voltage and comparing and outputting the equalizer output of B, it is possible to slice at the level of the zero crossing point of the eye pattern. The reference voltage levels 31a to 318 in FIG. 9B represent the reference voltage levels of each signal in D.

FIGS. 7, 29a to 29e show the levels of the reference voltages generated as described above, which coincide with the level of the zero crossing point of the eye pattern. If the comparison is output at a fixed level of 16, the pulse width will be Ta in case of a, causing phase jitter.

If reference voltages such as 292L to 29e are used, accurate pulse width T without phase jitter can be detected.

Therefore, the reference voltage generated in this way is applied to the comparator 1.
5 as a comparison voltage, the waveform equivalent output signals can be compared at the level of the zero crossing point of the eye pattern, and a pulse code train without phase jitter can be output. By inputting this pulse code string to the demodulator,
Since clock components can be detected stably and recorded data can be demodulated without read errors, a highly reliable optical recording/reproducing device can be provided.

Effects of the Invention As described above, the present invention includes a circuit that waveform-equalizes a reproduced signal from an optical disk, and a binarization of the waveform-equivalent output signal by detecting only a specific frequency component included in this waveform-equalized output signal. By generating a reference voltage for a comparator that performs Even if the level of the zero crossing point of the eye pattern of the waveform controller output signal changes due to a change in sensitivity, by matching the reference voltage of the comparator to the level of the zero crossing point of can be output.

By inputting this pulse code train to a demodulator, it is possible to stably detect the clock component and demodulate recorded data without read errors, making it possible to provide a highly reliable optical recording and reproducing device. There is a practical effect called a dog.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a conventional optical recording/reproducing device, Fig. 2 is a block diagram showing a part of the same device, and Fig. 3 is a block diagram showing a part of the same device.
The figure is a characteristic diagram showing the frequency characteristics of the recording and reproducing system of the same device, Figure 4 is a waveform diagram showing the eye pattern of the waveform equalizer output signal of the same device, and Figure 5 is a graph showing the time elapsed after recording by the same device. Figure 6 is a waveform diagram showing changes in the amplitude waveform of the preamplifier output, Figure 6 is a plan view showing changes in the bit shape after recording with the same device, and Figure 7 shows changes in the eye pattern after recording with the same device. 8 is a circuit diagram showing the configuration of a signal processing section of an optical recording/reproducing apparatus according to an embodiment of the present invention, and FIG. 9 is a waveform diagram for explaining the apparatus. 1...Semiconductor laser, 8...Optical disk, 14...Waveform fixtures, 15...Comparator, 21...Band pass filter, 23. 23'・
...Detection diode, 25, 25'...
...Capacitor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure θ Figure 3 S-type walk through the pregnant woman/I-Lesbian bag Figure 4

Claims (2)

[Claims] (1) A means for recording and reproducing signals by focusing a laser beam into a minute spot light and applying a thermal change to an optical disk, a waveform fixture for equalizing the waveform of the reproduced signal obtained from the optical disk, and this waveform, etc. An optical recording/reproducing apparatus comprising means for using a detection output of a specific frequency included in the output signal of the waveform equalizer as a reference voltage of a comparator that binarizes the output signal of the waveform equalizer. (2) The optical recording/reproducing device according to claim 1, which extracts the frequency component at the minimum inversion interval of the code included in the waveform equalized output signal using a bandpass filter. (3) Specifications included in the waveform equalized output 2. The optical recording and reproducing apparatus according to claim 1, wherein the reference voltage is generated by extracting the frequency of , and double-wave rectifying the extracted output.